(Adapted from the Applicant's Abstract) The specific aims are to provide rapid screening method for examining spatial expression patterns of differentially expressed genes to be cloned in Project 2; to permit Project 3 to localize the temporal and spatial patterns of expression of selected clones by both whole-mount and paraffin-section in situ hybridization; and to provide high quality and reproducible results for Projects 4, 5, and 6 and to prevent the unnecessary duplication of facilities and efforts among the subprojects that are involved.